It won't be on the official agenda. It might not even be asked out loud. But it may be the most important question during a congressional hearing Thursday on homegrown Islamic terrorists.

How should America talk about Muslim Americans?

Even in the tense months after the Sept. 11, 2001, terrorist attacks, public discussions of Islamic extremists were usually accompanied by a careful disclaimer that a peaceful religion had been hijacked.

But fueled by the Fort Hood massacre, controversy over a proposed Islamic center near Ground Zero and a series of high-profile arrests of homegrown terrorists, conservatives in particular have grown increasingly bold in criticizing Islam itself. They have objected to mosques, banned sharia (Islamic law) and attacked passages in the Koran.

On Thursday, the discussion about Muslims' place - and Muslims' obligations - in American society will move to Capitol Hill. The hearing, called by Rep. Peter T. King (R-N.Y.), could be a key moment in one of the country's angriest conversations.

"You can say things about this particular religion which you cannot say about any other religion in the United States of America," said Akbar Ahmed, a professor at American University.

Ahmed said the hearings could either encourage or defuse a growing sense of suspicion aimed at Muslims. "We were blind to it. And now that it's surfaced, and it's out there, I think we're at a very dangerous moment in American history," he said. "It's like a boil, and it needs to be pricked."

King's hearing will start Thursday morning in the high-arched, chandeliered hearing room of the House Committee on Homeland Security. The title is "The Extent of Radicalization in the American Muslim Community and That Community's Response."

Public opinion about Muslims hasn't changed much in recent years. In the fall, a Washington Post-ABC News poll asked whether mainstream Islam "encourages violence." Among all respondents, 31 percent said yes, slightly less than the recent high of 34 percent in 2003.

What's different now is the tone of the discussion - in Congress and across the country.

In Lieberman's hearings, most witnesses preceded their comments by saying that the problem was not Islam itself. That was an echo of what President George W. Bush said just days after 9/11, when he went to a D.C. mosque and declared, "Islam is peace." The president's remark and others that followed had the effect of constraining criticism.